Field of the Invention
This invention relates generally to a sensor for detecting cooling fluid that has leaked from a liquid cooled battery pack and, more particularly, to a sensor for detecting cooling fluid that has leaked from a liquid cooled battery pack on an electric vehicle, where the sensor includes a wire electrically coupled to a terminal of the battery pack that extends into an area where the leaked fluid may accumulate.
Discussion of the Related Art
Electric vehicles are rapidly gaining popularity in today's automotive marketplace. These vehicles include hybrid vehicles, such as the extended range electric vehicles (EREV) that combine a battery and a main power source, such as an internal combustion engine, fuel cell systems, etc., and electric only vehicles, such as the battery electric vehicles (BEV). Electric vehicles offer several desirable features, such as eliminating local emissions and usage of petroleum-based fuels at the consumer level, and potentially lower operating costs. Electric vehicle batteries can be of different battery types, such as lithium-ion, nickel-metal hydride, lead-acid, etc. A typical high voltage battery system for an electric vehicle may include a large number of battery cells or modules including several battery cells to meet the vehicle power and energy requirements. Maximizing battery pack performance and life are key considerations in the design and operation of electric vehicles.
In order to help maximize battery pack performance and durability, the temperature of the battery pack can be controlled. For certain types of battery packs, such as lithium-ion, it is known in the art to provide a thermal management system that flows a cooling fluid around the various battery cells in the battery pack to remove heat therefrom. Additionally, this thermal management system can include heaters to heat the cooling fluid, which in turn heats the battery to a desirable operating temperature during, for example, cold vehicle starts. The various flow channels and flow paths within the battery pack and battery enclosure are sealed so that the cooling fluid is contained in the proper area. However, as a result of many conditions, such as age, wear, temperature changes, etc., these flow channels may incur leaks, which causes the cooling fluid to flow out of the flow channels.
Fault isolation detection systems are sometimes employed in electrical circuits to provide electrical fault detection. Electric vehicles and electric hybrid vehicles include fault isolation circuits that isolate the high voltage of the battery from the remaining electrical components on the vehicle. Circuits are provided to monitor that isolation and if there is a breech in the isolation, warning signals can be provided to indicate the loss of isolation, including automatically shutting down the vehicle battery.
Many different types of fault isolation circuits exist in the art including both active isolation circuits and passive isolation circuits, where the isolation circuits may be internal to the battery circuit or external to the battery circuit. In order to provide electrical fault isolation, some vehicles are equipped with a battery disconnect unit (BDU) that automatically disconnects or removes battery power from the vehicle after a crash event by opening battery contactors. Also, it is known in the art to employ a manual service disconnect (MSD), which is a device that separates a battery into two parts, where a trained responder responding to a vehicle crash could remove the MSD to isolate the battery.
Because the cooling fluid that cools the battery pack may be conductive, loss of that cooling fluid may create conductive paths where loss of isolation may occur. Often, the electrical isolation circuitry in a vehicle is provided at an upper location in the battery enclosure and fluid that may have leaked from the thermal management system tends to collect in a lower area of the battery pack housing or container. Thus, that isolation circuitry may not detect a leak until the fluid level has reached a significantly high level, which is typically not desirable.